Simple external antenna attenuation for outdoor SWLing

Saturday, November 12, 2016

I recently purchased a Sony ICF-SW100 after reading multiple glowing reviews of it on eHam and the SWLing post. It's a great little shortwave radio that can easily fit into a jacket pocket. The unit has an external antenna input together with a DX/Local switch that adjusts the radio's sensitivity. However, after using the radio outdoors for several days I have found that the DX setting is just a little too sensitive when using it with the long wire antenna (resulting in distortion on some medium-strength signals), while the Local setting isn't very sensitive at all (meaning that some of these signals can only be heard very faintly).

It turns out that this problem can be solved by using a variable attenuator available in Maplin. The attenuator's specifications state that it has a 2dB — 20dB range and that it operates from 5MHz upwards. However, I have tested it with the ICF-SW100 as well as with my other radios, and I have found that it works very effectively all the way down to long wave. With some additional cable accessories, it's possible to insert the attenuator between ICF-SW100's external antenna input and the long wire as follows:

When I head out in the morning not knowing if I can get any free time later in the day to SWL outdoors, I take the following "opportunistic DXing kit" with me:

That's the Sony ICF-SW100, a Sony ICD-PX333 recorder, the Maplin variable attenuator with all the cable accessories, an audio volume attenuation cable (for connecting the recorder to the radio's line output), and the long wire antenna.

I am quite pleased with ICF-SW100's performance so far, and with this simple and cheap attenuator it's possible to get even more out of this radio in challenging reception conditions.

About the author

This blog is written by a shortwave radio enthusiast based in London, UK. You can follow him on Twitter at @LondonShortwave